The present invention relates to a rotary lift table and a device for forming stacks of flat objects, in particular of print products.
Rotary lift tables for processing flat objects, in particular print products such as printed leaflets, newspapers, magazines, etc., are generally known. They are equipped with a rotatable and/or liftable and lowerable rotary lift table board on or above which the flat objects come to lie. Rotary lift tables generally have assigned discharge means, by means of which the flat objects lying on the rotary lift table board can be pushed out in a selected discharge direction.
The rotatability of the rotary lift table board is particularly advantageous in the formation of stacks of folded print products. To improve the stability of such stacks, partial stacks respectively rotated in relation to one another by 180° relative to a rotational axis oriented at a right angle to the rotary lift table board are layered alternately on top of one another. In this manner, thicker regions on the fold side and thinner regions of the free lateral edges of print products of consecutive partial stacks respectively come to lie on top of one another in an alternating manner so that height differences between the individual partial stacks are equalized due to their regionally different thicknesses.
The rotary lift table board is furthermore preferably of liftable and lowerable design in order, for example, to selectively reduce heights of fall for print products or partial stacks formed therefrom or, for the purpose of compressing stacks, in order to be able to press these against press elements arranged above the rotary lift table board.
The configuration both of the rotatability as well as the liftability and lowerability of the rotary lift table board is not absolutely essential in every case. Rather, the rotary lift table described and claimed below can also be employed in a completely analogous manner with a restricted functionality, i.e. in the case of use as a rotary table, lift table or also only as a stacking table.
A rotary table for stacking print products is, for example, described in U.S. Pat. No. 4,068,567. Therein, a rotary table board is arranged on a hydro-pneumatic rotatable foot, said rotary table board being equipped on two opposing sides with discharge devices which have discharge means for discharging the print products arranged in stacks. Therein, a movement of the discharge means beyond the rotary table board and displacing the print products defines a discharge direction. The rotary table board is groove-like or arched in a V-shape towards the bottom. Planar bearing surface elements, on which a lower print product comes to lie, are formed on both sides of a lower edge line running parallel to the discharge direction. The print products lying on the rotary table board are adapted to the concave arch of the rotary table board due to their surface-like configuration and their dead weight.
The problem arises particularly in the case of large-format and very thin print products that the dimensional stability of stacks of such print products is so low during discharge that undesirable dimensional changes to the stack and damage to the print products can occur.
An object of the present invention therefore lies in further improving the dimensional stability of stacks of flat objects during their formation or their removal from a rotary lift table.